In a hybrid wheel loader in the known art, an engine and a motor are used as a motive power sources. During excavation work or loading work, which such a hybrid wheel loader performs by using its bucket, it may require a drive force greater than that required for traveling operation. As a means for addressing this need, a dynamo-electric motor also fulfilling a function as a generator is utilized in the known art (see, for instance, patent literature 1). In this type of hybrid wheel loader, electrical energy generated by the generator is charged into a capacitor (electricity storage device) while the accelerator is in an off state and the dynamo-electric motor is driven as a motor during excavating or loading via the electricity storage device having been charged, so as to supplement the drive power provided by the engine.
The hybrid wheel loader disclosed in the prior art literature cited above includes a gear train disposed between the engine and a torque converter, with the dynamo-electric motor also functioning as a generator (motor/generator) mounted coaxially with the output shaft of the gear train.